The manufacture of metallic sandwich structures may require joining one or more sandwich panels together in order to form the desired sandwich structure. During the fabrication process, fusion welding is one method that may be used to securely join sandwich panels together. During fusion welding of the weld joint it is extremely important that the molten and solidifying weld pool and adjoining heat-affected zone are properly shielded in an inert gas to prevent reaction with air and other non-inert or reactive material. In many welded structure designs, adequate access to both sides of the weld joint may allow for a sufficient delivery of purge gas before, during and after the welding process. However, structures incorporating sandwich panels may have internal cell structures that provide limited access to the front and/or back side of the weld joint. This limited access may make it increasingly difficult to properly purge the weld joint area and inspect weld quality.